• July 2021

    John Farrell • 07/22/2021 at 23:50 • 0 comments

    Where do I start...

    First off, this project is not dead! Although it may seem like it, there is still a pulse over here.

    A lot has happened in the last two years for me, so updates and progress have been slow. I have made some progress though! Unfortunately it is only hardware progress and the software is still in the same state, but that does mean I have some cool pictures to share so hopefully that makes up for it.

    Hardware

    There main update here is that I have fleshed out the design of the upper portion of the mount and 3D printed roughly half of it. I have also printed the the bottom half of the second worm drive. Between these, we have an actual two axis assembly made!

    You should recognize the worm drive in black from my first project log.

    Don't worry, there's more pictures at the end showing some different angles.

    As you can see, I designed the 'barrel' of the mount to utilize the same worm drive assembly for both axes. This saved me design time and allowed me to get started on other stuff. You should also notice the cup towards the end of the barrel in the other pictures. When the other half is printed, this will form a nice seat for the counterweight rod.

    In the end, the mount will look like a bullet with two disks attached to it and a rod coming through it. This is pretty similar to other equatorial mounts you'll see out there, so it's nothing too crazy.

    Looking at the side view picture below, you may ask why the other drive is sticking out so far? Well, I was dumb and just stuck the motor way out on the side with no concern for anything else, and that's the result. There is just enough room for the base motor to spin all the way around without stopping, so full circles can be made no problem.

    The motors weigh a lot more than I expected since I had never dealt with them before, so the moment about the axis of rotation for each axis is pretty significant. Without any energy in the system, there is more than enough force to spin the base motor around with just the weight of the top. Hopefully when the rest of this is printed and I get the counterweight situation figured out this will be less noticeable, but it's something to think about from my end at least.

    Unfortunately my student Inventor license ran out so I can't access my regular files, so it will take a bit of time to convert everything over to a more open license. This means I can't show you guys any 3D models for the barrel just yet unfortunately. I do have the top half and the end cap all ready to print however, so it is coming along!

    I have also decided to build my own tripod for this mount. I have designed it all in the same material using 3/4" EMT conduit. This should provide a nice sturdy base for this system. I am also going to use that same material for the counterweight rod. There is a lot of material going into this project, so I hope it doesn't end up being too heavy to actually move around.

    I don't have any pictures of the mount as I haven't assembled it or anything just yet, but hopefully you all will see that soon.

    Software

    Unfortunately this is the same situation as last time. No update here. The design idea is still the same with one Arduino focused on doing motor control logic and one focused on doing math and GPS calculations and all the other fun stuff. The two will be talking using standard serial communications with a super simple protocol that I will get around to building.

    I also plan to have this thing controllable through Stellarium, so there will be some sort of USB serial as well.

    Future Plans

    Since I have graduated school and am working full time, I don't have as much time to dedicate towards this project. However, I do plan on posting monthly updates from here on out even if I haven't really made any progress that month, just to keep everyone informed.

    That's it for now! Hopefully next time you hear from me I have made a lot of progress on this thing!

    Pictures

    ---

    Rear view of the mount assembly showing the barrel and two worm drives.

    ---

    Side view of the mount....

    Read more »

  • November 2019

    John Farrell • 11/27/2019 at 17:15 • 0 comments

    First update of the project! We are now officially WIP instead of researching.

    Alt/Az to GEM

    I've decided to transition the type of mount to a German Equatorial Mount (GEM) instead of an Alt/Az mount. I chose to do this for a few reasons. After writing the software that converts Ra/Dec coordinates into Alt/Az coordinates, I realized it takes quite a bit of operations, and can be pretty intensive to calculate quickly. This can make tracking less accurate over time. With an equatorial mount, I can directly use the Ra/Dec coordinates with much less calculations, allowing me to update the tracking location more frequently.

    This also has the added benefit of only requiring one drive to move the scope, instead of driving both. This is one of the main benefits of using a GEM mount, and why most motorized mounts you see are of this design.

    Main Worm Drive

    Over the past few weeks, I have been working on designing various parts and haven't posted any updates. I have finished the design of the main drive for both axis. Here is a link to the Reddit post I made showing the inner workings of it. It uses a few parts, and they are all listed at Thingiverse here where you can get the STL files if you want to print them, along with as mall description.

    Arduino Stepper Hat

    To drive both steppers, I am using a StepperOnline 2A bipolar stepper. These give me 84oz/in of torque, which combined with the 15:1 gear ratio of the worm drive should give me more than enough torque necessary to move the weight of most telescopes.

    To drive the steppers, I went with the traditional A4988 driver. I will probably upgrade this in the future as the A4988 has a max current of 2A and I would like some degree of excess in that.

    I made an Arduino UNO hat to interface with these:


    I haven't made any digital schematics of this, but I do plan on it.

    Controller Interface

    To control the tracking and whatnot, I've designed a handheld controller to interface with the Arduino controlling the motors. As with the Arduino hat, I haven't made any digital schematics of this, but I will post those in a later update, along with the code when I finish it. With this, you will be able to select an object from a database that you want to track, control individual axii', and whatever else I want.